Area Forecast Discussion
Issued by NWS Mt. Holly, NJ

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000 FXUS61 KPHI 291953 AFDPHI AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE MOUNT HOLLY NJ 353 PM EDT FRI AUG 29 2014 .SYNOPSIS...
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HIGH PRESSURE SITUATED OVER THE NORTHEAST WILL MOVE OFFSHORE TONIGHT...MAKING WAY FOR A WARM FRONTAL PASSAGE SATURDAY NIGHT. THIS WARM FRONT WILL BECOME A QUASI-STATIONARY BOUNDARY NEAR THE CANADIAN BORDER DURING THE SUNDAY THROUGH TUESDAY TIMEFRAME...A TROUGH OF LOW PRESSURE WILL EXTEND SOUTHWARD FROM THIS BOUNDARY TO THE EAST OF THE APPALACHIANS...BETWEEN A BERMUDA HIGH PRESSURE ANCHORED TO THE EAST AND SLOW MOVING COLD FRONT IN THE MISSISSIPPI VALLEY. THIS COLD FRONT IS PROJECTED MOVE THROUGH THE REGION LATE TUESDAY INTO EARLY WEDNESDAY...FOLLOWED BY HIGH PRESSURE ON THURSDAY.
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&& .NEAR TERM /UNTIL 6 AM SATURDAY MORNING/...
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UPPER LEVEL TROUGH SLIDES OVER THE REGION TONIGHT, LEAVING THE REGION UNDER CLEARING SKIES. THE COMBINATION OF MID AND UPPER LEVEL SUBSIDENCE, WEAK ON SHORE/UPSLOPE FLOW, AND CLEARING SKIES COULD SUPPORT PATCHY FOG DEVELOPMENT ACROSS THE REGION. ONE LIMITING FACTOR HOWEVER, IS THAT DEW POINTS REMAIN RELATIVELY LOW (IN THE 40S AND LOW 50S). THUS, NOT ANTICIPATING ANYTHING WIDESPREAD OR PARTICULARLY DENSE AT THIS TIME. LOWS COULD BE A BIT TRICKY DEPENDING ON HOW MUCH AND HOW QUICKLY MOISTURE ADVECTION TAKES PLACE TONIGHT. GIVEN HOW WEAK THE FLOW IS, THINK WE WILL BE ABLE TO HAVE AT LEAST A FEW HOURS OF PRIME RADIATIONAL COOLING CONDITIONS THROUGH LATE THIS EVENING, BEFORE INCREASING MOISTURE HELPS TO LEVEL OFF THE TEMPERATURE TRENDS.
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&& .SHORT TERM /6 AM SATURDAY MORNING THROUGH 6 PM SATURDAY/...
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WINDS WILL SHIFT TO SOUTHERLY AND INCREASE BY AT LEAST MID MORNING. THIS WARM AIR ADVECTION WILL RESULT IN MAX TEMPS A FEW DEGREES HIGHER THAN TODAY, EVEN IN SPITE OF ANY PATCHY FOG THAT MAY LINGER INTO THE MID MORNING HOURS.
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&& .LONG TERM /SATURDAY NIGHT THROUGH FRIDAY/...
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HEMISPHERIC MODEL ANALYSIS SHOWS SOUTHEAST U.S. RIDGING WITH WEAK TROUGHING NORTH OF THE GREAT LAKES AND MID-WEST AT THE START OF THE LONGTERM. BETTER TROUGHING ACROSS THE WESTERN U.S. MOVES EASTWARD EVENTUALLY CARVING INTO THE TOP OF THE SOUTHEAST RIDGE BY EARLY NEXT WEEK. THE PREVAILING SOUTHWEST FLOW ALOFT DECREASES, ULTIMATELY BECOMING MORE ZONAL, AS THE NORTHERN STREAM OF THE JET MOVES TO THE NORTH OF OUR REGION LATE IN THE PERIOD. SUNDAY - TUESDAY...SLOW SAGGING BOUNDARY TO THE NORTHWEST OF THE REGION SLOWS EVEN FURTHER AND MORE THAN LIKELY BECOMES PSEUDO-STATIONARY WITH STRONG RIDGING TO OUR SOUTHEAST. MID AND UPPER LEVEL FLOW, BEING SOUTHWESTERLY, KEEP THIS BOUNDARY DRAPED JUST TO OUR NORTHWEST AS WARM AND MOIST GOMEX AIR IS PUMPED INTO THE REGION. MULTIPLE MID-LEVELS WAVES, WITH WEAK SURFACE TROUGHS, TRAVERSE THE REGION EACH DAY PROVIDING CHANCES OF SHOWERS AND THUNDERSTORMS. THE BEST CHANCES FOR CONVECTION CONTINUES TO HONE IN ON THE SUNDAY NIGHT INTO MONDAY TIMEFRAME AS THE STRONGEST OF THE MID-LEVEL WAVES MOVES THROUGH. AFTERWARDS, HIGHER THAN NORMAL PWAT AIRMASS, POSSIBLY EXCEEDING 2 INCHES, AND AMPLE INSTABILITY EACH AFTERNOON SHOULD ALLOW FOR DIURNALLY DRIVEN CONVECTION. TEMPERATURES AND UNFORTUNATELY THE DEWPOINTS WILL BE ON THE INCREASE THIS TIMEFRAME MAKING CONDITIONS FEEL TRULY LIKE AN EARLY AUGUST DAY, IN EARLY SEPTEMBER. WEDNESDAY...LOW PRESSURE SYSTEM WELL TO THE NORTH OF THE REGION SENDS A SOMEWHAT STRONGER COLD FRONT TOWARDS OUR AREA. RIDGING TO OUR SOUTH SHOULD PREVENT A QUICK PASSAGE, BUT NONE-THE-LESS WE CURRENTLY EXPECT THE FRONT TO CLEAR OR BECOME WASHED OUT LATER IN THE DAY. STILL HAVE SOME LOW-END CHANCES, MOSTLY NORTH, WITH THIS FRONT THOUGH IT CONTINUES TO LOSE STEAM RUNNING INTO THE BUILDING RIDGE TO OUR SOUTH. WE SHOULD BE DRYING OUT NORTH TO SOUTH BY THE AFTERNOON HOURS WITH LOWERING OF THE DEWPOINTS...TEMPERATURES SHOULD STILL BE IN THE UPPER-80S. THURSDAY - FRIDAY...HIGH PRESSURE CONTINUES TO BUILD BACK INTO OUR REGION WITH ZONAL FLOW ALOFT. THERE DOES NOT LOOK TO BE MUCH IN THE WAY OF MID-LEVEL FORCING FROM ANY OF THE PASSING SHORTWAVES, MOST OF THE ENERGY STAYS WELL TO OUR NORTH...WE SHOULD BE DRY BOTH DAYS. TEMPERATURES WILL VENTURE BACK DOWN INTO THE NORMAL RANGE WITH CONTINUED DEWPOINT LOWERING.
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&& .AVIATION /20Z FRIDAY THROUGH WEDNESDAY/...
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THE FOLLOWING DISCUSSION IS FOR KPHL, KPNE, KTTN, KABE, KRDG, KILG, KMIV, KACY AND SURROUNDING AREAS. VFR CONDITIONS SHOULD CONTINUE THROUGH AT LEAST 06Z, WITH ONLY HIGH CIRRUS CLOUDS FOR MOST OF THE REGION, WHILE SCT TO BKN MID LEVEL CLOUDS (050) PERSIST NEAR THE JERSEY SHORE THROUGH 00Z (INCLUDING KACY AND KMIV). AFTER 06Z...THERE IS A CHANCE THAT PATCHY FOG COULD DEVELOP. VERY WEAK ON SHORE FLOW, SUBSIDENCE IN THE MID AND UPPER LEVELS, AND CLEARING SKIES WILL PROMOTE FOG DEVELOPMENT. ON THE OTHER HAND HOWEVER, DEWPOINTS ACROSS THE REGION REMAIN RELATIVELY LOW (IN THE 40S AND LOW 50S) DESPITE SOME MODEST MOISTURE ADVECTION. AS WEAK AS THE LOW LEVEL FLOW IS, IT IS DOUBTFUL ENOUGH MOISTURE WILL ADVECT INTO THE REGION BY TONIGHT TO SUPPORT WIDESPREAD FOG. FOR NOW, EXPECT THE HIGHEST THREAT OF FOG TO BE NEAR THE COAST (KACY AND KMIV) AND AT KABE AND KRDG WHICH ARE STARTING OUT WITH SLIGHTLY HIGHER DEW POINTS THAN THE REST OF THE REGION. ALSO, IF THE WINDS CONSISTENTLY STAY SOUTHEASTERLY, THE THREAT AT KILG WOULD INCREASE THANKS TO THE MOIST FETCH ALONG THE BAY. GIVEN THE UNCERTAINTIES WITH THE MOISTURE ADVECTION, HAVE INCLUDED VISIBILITIES ONLY AS LOW AS MVFR. AT THIS TIME, FOG OR BR DEVELOPMENT APPEARS VERY UNLIKELY AT KPHL, KPNE, AND KTTN. CONDITIONS SHOULD RETURN TO VFR BY MID MORNING AS SOUTHERLY WINDS INCREASE. OUTLOOK... SUNDAY...VFR. SCATTERED SHOWERS AND THUNDERSTORMS NORTH AND WEST OF PHL. MDT CONFIDENCE. MONDAY - WEDNESDAY...VFR. SCATTERED SHOWERS AND THUNDERSTORMS POSSIBLE EVERYWHERE. LOW TO MDT CONFIDENCE ON PRECIP COVERAGE.
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&& .MARINE...
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WAVE HEIGHTS SHOULD REMAIN 2 TO 4 FEET, AND WINDS LESS THAN 20KT, THUS CONDITIONS SHOULD REMAIN BELOW SMALL CRAFT ADVISORY CRITERIA. PATCHY FOG MAY DEVELOP SATURDAY MORNING ON THE DELAWARE BAY, ESPECIALLY THE UPPER BAY, BUT SHOULD DISSIPATE BY LATE MORNING AS WINDS INCREASE. OUTLOOK... SUNDAY - WEDNESDAY...SUB-SCA CONDITIONS EXPECTED ACROSS OUR WATERS WITH HIGH PRESSURE OFFSHORE. COLD FRONT WILL APPROACH MONDAY AND TUESDAY EVENTUALLY CROSSING ON WEDNESDAY. WINDS WILL BACK TOWARDS THE SOUTHWEST ON SUNDAY AND REMAIN THAT WAY THROUGH TUESDAY. SEAS WILL INCREASE BUT REMAIN BELOW SCA AT THIS TIME.
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&& .RIP CURRENTS...
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RESIDUAL SWELLS FROM CRISTOBAL WILL CONTINUE TO AFFECT THE COASTS OF DELAWARE AND NEW JERSEY INTO THIS EVENING. THUS, THE MODERATE RISK FOR RIP CURRENTS CONTINUES.
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&& .PHI WATCHES/WARNINGS/ADVISORIES... PA...NONE. NJ...NONE. DE...NONE. MD...NONE. MARINE...NONE. && $$ SYNOPSIS...FRANCK NEAR TERM...JOHNSON SHORT TERM...JOHNSON LONG TERM...HEAVENER AVIATION...HEAVENER/JOHNSON MARINE...HEAVENER/JOHNSON RIP CURRENTS...JOHNSON

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